Bladder outlet obstruction is one of the most commonly encountered disorders in urology. The most frequently occurring anatomical cause of bladder outlet obstruction in males is enlargement of the prostate gland, either by hypertrophy or hyperplasia. The prostate is a chestnut-sized gland lying inferior to the bladder and surrounding approximately the first inch of the urethra. In older males, it is not uncommon for a progressive enlargement of the prostate to constrict the prostatic urethra. This condition, known as benign prostatic hyperplasia, can cause a variety of obstructive symptoms, including urinary hesitancy, straining to void, decreased size and force of the urinary stream, and, in extreme cases, complete urinary retention possibly leading to renal failure. A number of irritative symptoms may also be experienced, including urinary frequency and urgency, nocturnal incontinence, and discomfort.
When intervention is indicated, there has heretofore been no widely accepted alternative to surgery. The preferred surgical procedure is the transurethral resection, wherein a resectoscope is inserted through the external opening of the urethra, and an electrosurgical loop is employed to cut away sections of the prostate gland from within the prostatic urethra. However, many patients are poor candidates for transurethral resection. Contraindications for this surgery may include cardiac problems or inability to undergo anesthesia. Also, the patient may have elective reasons for needing to postpone surgery. Thus, there is a need to provide a mechanism for the management of bladder outlet obstruction in those patients where surgical intervention is inappropriate.
Efforts have been made to provide a nonsurgical modality for the management of bladder outlet obstruction resulting from prostatic hypertrophy and hyperplasia. One such example is found in U.S. Pat. No. 4,762,128, which discloses an expandable tubular urethral stent. The stent includes a perforated expandable central section comprised of a malleable metal to permit expansion of the central section and to hold its expanded configuration under pressure. The stent is adapted for transurethral insertion via the external opening of the urethra and for placement within a stenotic region of the urethral lumen caused by a hypertrophied prostate gland. When the stent is properly positioned, an expansion catheter is inflated within the stent, thereby causing the expandable central section of the stent to deform outwardly, thereby ensuring patency of the lumen.
However, the expandable stent of the aforementioned U.S. Pat. No. 4,762,128 has not gained widespread acceptance because of the fear that the tissue of the urethral walls, under pressure from the enlarged prostate, will penetrate the perforations of the expanded central section of the stent. The more the stent is expanded, the larger the perforations become, and the greater the pressure exerted between the expanded stent and the enlarged prostate. Under these conditions, the tissue of the urethral walls would tend to penetrate even more deeply into the perforations of the stent and thereby render the stent difficult, if not impossible, to remove without major surgery.
Another example of a nonsurgical modality for the management of bladder outlet obstruction is the Prostakath.RTM. intraurethral catheter. This device comprises a short, gold-plated metal helix or spiral which is tapered at one end and terminates in a loop at the other. The metal spiral is endoscopically placed within the stenosed region of the prostatic urethra to reinforce the lumen. Again, however, this device has not gained widespread acceptance, largely because of concerns regarding encrustation of the metal spiral which may cause the spiral to adhere to the urethral walls, thereby necessitating surgery to remove the device. In addition, there have been reservations that the tip of the spring may cause bladder irritation. Finally, there have been concerns that attempts to remove the metal spiral by endoscopically pulling on its distal end may cause the spiral to unwind such that the sharp end of the wire lacerates the urethra.